脑动静脉畸形的生物力学研究：基于四维血流磁共振成像和复合手术的实验与建模

Cerebral arteriovenous malformations (AVM) are vascular abnormalities consisting of direct connections from arteries to veins through an intervening network of low resistance vessels called the nidus thereby resulting in disrupted hemodynamics and a risk of intracranial hemorrhage. Surgical cutting and interventional occlusion are two therapy methods to AVM and they may also induce oedema and multifocal hemorrhage. It is general agreement that the rupture bleeding of AVM has very close relationship with the cerebrovascular hemodynamics. Two theories have been proposed to explain the mechanism of bleeding of cerebral AVM after treatment, one is “normal perfusion pressure breakthrough” and the other is “occlusive hyperaemia”. However, both theories need more evidence to prove. A reasonable biomechanics model is very desired to study the bleeding mechanism of cerebral AVM. A biomechanics model with elastic wall, patient-specific geometry and boundary conditions will be established based on the hybrid operation and 4D flow MRI in this project. Using this biomechanical model, the blood flow in 30 AVM cases before and after treatment will be simulated numerically. By analyzing the hemodynamic parameters such as pressure, wall shear stress, axial stress and strain, circumferential stress and strain, the hemodynamics mechanism of oedema and multifocal hemorrhage after cerebral AVM treatment will be proposed, which will benefit to the treatment planning in clinic.

脑动静脉畸形是一种常见的脑血管疾病，它是动脉不经毛细血管床直接引流至静脉形成畸形血管团，而畸形团存在很高的破裂风险。脑动脉畸形的主要治疗方式是介入栓塞和手术切除，但是治疗后也存在脑组织水肿和出血的并发症。目前普遍认为脑动静脉畸形术后破裂出血与血流动力学的变化密切相关，已经有正常灌注压突破与阻塞性出血两种理论进行解释，但是尚缺乏足够的证据。因此，建立一个合理的生物力学模型研究脑动静脉畸形具有重要的理论价值和临床价值。本项目利用复合手术的优势获得脑动静脉畸形的组织样本并进行力学性能测试；利用四维血流磁共振成像技术在体测量脑血管内的血流速度；建立具有弹性血管壁、个性化几何形态和边界条件的脑动静脉畸形的生物力学模型；利用该模型数值模拟30例脑动静脉畸形病人的栓塞或手术切除前后的血液流动，分析畸形团在治疗后出现破裂出血的血流动力学机制，为脑动静脉畸形的治疗和手术规划提供依据。

脑动静脉畸形是一种常见的脑血管疾病，它是动脉不经毛细血管床直接引流至静脉形成畸形血管团，而畸形团存在很高的破裂风险。脑动脉畸形的主要治疗方式是介入栓塞和手术切除，但是治疗后也存在脑组织水肿和出血的并发症。建立一个合理的数值仿真模型研究脑动静脉畸形具有重要的理论价值和临床价值。本项目利用CTA影像和MRA影像建立了脑动静脉畸形的计算流体力学仿真模型，利用多相流模型建立了注射Onyx胶栓塞脑动静脉畸形的数值仿真模型。多相流模拟了Onyx胶和血液之间的相互作用，并且模拟了Onyx胶的凝固过程。利用临床造影的动态图像对这一仿真模型进行了验证，并进一步利用该模型模拟病人的栓塞方案并讨论了临床上较为关注的问题，包括栓塞剂注射的位置与栓塞效果的关系以及多次栓塞时不同栓塞阶段引流静脉血流量的变化，这些都是临床上非常关心和关注的问题。这一模型的建立使脑动静脉畸形的手术规划的实施成为了可能，也为进一步优化脑动静脉畸形介入栓塞提供了可使用的模型。